Bootstrap/Load: Fix fatal error when passing a `WP_Error` to `wp_die()`.

This was introduced in [44466]. Also, this changeset adds tests for `_wp_die_process_input()` so that this never happens again.

Props dd32.
See #45933.

Built from https://develop.svn.wordpress.org/trunk@44690


git-svn-id: http://core.svn.wordpress.org/trunk@44521 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/functions.php

@@ -3374,7 +3374,7 @@ function _wp_die_process_input( $message, $title = '', $args = array() ) {
 					$errors[] = array(
 						'code'    => $error_code,
 						'message' => $error_message,
-						'data'    => $error->get_error_data( $error_code ),
+						'data'    => $message->get_error_data( $error_code ),
 					);
 				}
 			}

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.1-beta2-44689';
+$wp_version = '5.1-beta2-44690';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.